More and more printing is done in color, which is more expensive than printing in black and white. Customers are looking for more cost effective alternatives. One such alternative is to print only selected pages of a document in color while remaining pages are printed in black and white.
Two conventional methods for printing selected pages in color are practiced today: manual and automatic. The manual method creates the entire document, including color pages, assigning page numbers, annotations, etc., and then manually and electronically splits the job into two separate files, one for color printing, one for black and white. Splitting results in three separate versions of the original electronic document that must be maintained along with the original file: the initial combined version, the split-off color-printing portion, and the split-off black and white portion. If a content change is required, all three electronic documents frequently must be re-created from the original file. This method works well, but it is cumbersome and time-consuming. In other words, an initial computer file is separated into to other computer files, one for color and one for black and white.
The automatic method uses an algorithm to analyze the actual image data in order to identify either RGB or CMYK color content. The automatic method sets a threshold level for the color content, and uses its algorithm together with the threshold level to route pages automatically either to a black and white printer or a color printer. This method can be very productive, but the accuracy of the algorithm is limited, resulting in black and white pages being printed on the color device or vice versa. Furthermore, this method requires additional hardware and software which can add significant extra cost. Even when the automatic method works well, the printing process is relatively slow. Where color and black and white print engines are in one machine, one engine is idle while the other is printing. Black and white documents print quicker than color documents. If a machine is tasked with printing both color and black and white, the color prints will consume a substantial amount of time during which the black and white print engine is idle.